Signal generating apparatus

ABSTRACT

A signal generating apparatus comprising a bistable magnetic device which alters its magnetic state when the density of magnetic flux to which it is subject passes through a predetermined value, and detecting means providing an output signal responsive to a change of magnetic state of the bistable device. A conducting means for magnetic flux subjects the bistable magnetic device to magnetic flux conducted therethrough and comprises a first portion providing a path of high permeability and a second portion providing a path of alterable permeance for varying the reluctance of the conducting means and the density of magnetic flux to which the bistable device is subject. An energizing means provides a controllable magnetic field for inducing magnetic flux in the conducting means and provides a flux density sufficient to alter the state of the bistable device with the variation of reluctance of the conducting means.

The invention relates to a signal generating apparatus, and moreparticularly to an apparatus for generating signals for selected angularpositions of a rotary member.

Automobile engine ignition systems provide timed sparks to theircylinders for igniting their fuel mixture at specific times during theircombustion cycles. Such systems utilize a low voltage primary circuitwhich includes a battery, an ignition timing switch with a pair ofbreaker points actuated by the breaker cam shaft of an engine, acapacitor connected across the breaker points, and the primary windingof an ignition coil. A high voltage secondary circuit is provided by themany turns of the secondary winding of the ignition coil, a rotarydistributor switch, and the spark plugs received by the cylinders of theengine.

In operation, when the breaker points of the switch are closed, currentflows from the battery through the breaker points and the primarywinding of the ignition coil. The current through the primary windinginduces magnetic flux around the ignition coil. The opening of thebreaker points is timed by the rotation of the engine. This opens thecircuit through the switch, causing current to flow into the capacitorand rapidly decrease in the primary winding of the coil. This results inthe rapid collapse of flux about the induction coil inducing a highvoltage in the secondary winding, which is delivered by the distributorswitch to the spark plug of a selected cylinder of the engine. In thismanner high voltage timed signals are generated and delivered to each ofthe spark plugs in the required sequence for proper operation of theengine.

The breaker points open to deliver the high voltage signal to the sparkplug of a cylinder at a time before maximum compression of combustablefuel. The exact time at which the spark is delivered for optimumoperation of the engine depends upon the engine speed and load. The"timing" of the opening of the breaker points is advanced or madeearlier at high engine speed, and is usually activated by centrifugalforce provided by small weights which are driven by the breaker camshaft.

Improvements have been made in the conventional ignition systemdescribed, by providing a solid state switching device, such as atransistor, in place of the breaker points. The transistor is capable ofinterrupting the primary current without wearing or burning which aremajor defects of the mechanical breaker point type of distributors. Inanother form of device, the breaker points, or other triggering devicesbased upon magnetic and optical effects, are still used but only tocontrol the transistor. In such devices, only a small control current isrequired compared to the current in the primary circuit.

In addition to the above ignition systems, a current discharge systemhas been utilized in which a capacitor is charged to several hundredvolts. When an ignition spark is required, the capacitor is dischargedthrough the primary winding of the ignition coil. A switching transistorwhich is controlled by breaker points, or other triggering devices, isturned on to deliver the capacitor current to the primary winding of theinduction coil. The sudden applications of high current to the primarywinding produce high voltage signals in the secondary winding which aredelivered to the spark plugs as described above.

The present invention relates to a signal generating means which, amongmany other uses, may be utilized for providing highly accurate andcontrolled timing signals for activating a switch or transistor toproduce high voltage signals for delivery by a distributor which may beof the conventional type, to the spark plugs of an internal combustionengine. The signal generating means provides output signals which aredeliverable at selected angular positions of a rotary member and are notdependent upon the rotational rate or speed at which it is operated. Theoutput signals may also be easily controlled and advanced by anelectrical control signal.

It is, therefore, an object of the present invention to provide a newand improved signal generating means for providing timed output signals.

Another object of the present invention is to provide a new and improvedsignal generating apparatus for providing timing signals for abreakerless automobile ignition system.

Another object of the present invention is to provide a new and improvedsignal generating apparatus for providing timing signals at selectedangular positions of a rotary member and which may be controlled foradvancing or retarding selected output signals.

Another object of the present invention is to provide a new and improvedrotary signal generating apparatus which provides an output signal whichis a selected function of its rotary position.

Another object of the present invention is to provide a new and improvedsignal generating apparatus utilizing a bistable magnetic device as anelectronic position sensor for providing signals for an ignition systemof an internal combustion engine.

Another object of the present invention is to provide a new and improvedsignal generating apparatus for sensing shaft positions of rotarydevices.

Another object of the present invention is to provide a new and improvedsignal generating apparatus of high efficiency, reliability anddurability.

The above objects and advantages, as well as many other advantages areachieved by providing a signal generating apparatus comprising abistable magnetic device which alters its magnetic state when thedensity of magnetic flux to which it is subject passes through apredetermined value. A conducting means for magnetic flux subjects thebistable magnetic device to conducted magnetic flux with a density whichpasses through the predetermined value for altering the state of thebistable magnetic device. The conducting means includes a first portionproviding a path of high permeability, and the second portion providinga path of alterable permeance, for varying the reluctance of theconducting means and the density of the magnetic flux to which thebistable device is subject. An energizing means having an energizingcoil would about the first portion of the conducting means provides acontrollable magnetic field for producing magnetic flux in theconducting means for providing a flux density sufficient to alter thestate of the bistable device with variation of reluctance of theconducting means. A detecting means provides an output signal responsiveto each change in the magnetic state of the bistable device.

The path of alterable permeance of the second portion of the conductingmeans, in one form, is provided by a rotatable member having at leastone element of high permeability, which provides a minimum value ofreluctance when it is in one of its angular positions and a maximumvalue of reluctance when it is in another angular position displacedfrom the first position. The member provides reluctance values varyingbetween the minimum and maximum values as a continuous function of itsangular position. The energizing means comprises an energizing sourcewhich provides direct current to the energizing coil, with the value ofthe direct current being adjustable for determining the angular positionof the member at which the bistable device is subject to thepredetermined value of flux density for altering its magnetic state andfor which the detecting means provides an output signal.

The signal generating apparatus is particularly useful for producingtiming signals for an ignition system of an internal combustion engine.The member is provided with a shaft which is adapted for being rotatablydriven in synchronism with the crank shaft of the internal combustionengine to provide spark timing signals derived from the detecting means.The energizing source varies the value of direct current provided to theenergizing coil for advancing and retarding the occurrence of outputsignals of the detecting means with respect to the angular position ofthe member for being responsive to the spark timing requirements of theinternal combustion engine.

In another use, the signal generating means provides output signalswhich indicate the angular position of a rotatable member, and thegenerating means can be adjusted so that output signals are provided forselected angular positions of a rotatable member, as well as providingmarker signals for indicating the first of a plurality of outputsignals. In such uses an advantage of the signal generating apparatus isthat neither the amplitude nor timing of the output signals is effectedby the speed or rate of angular rotation of the rotary member.

The foregoing and other objects of the invention will become moreapparent as the following detailed description of the invention is readin conjunction with the drawings in which:

FIG. 1 is a diagrammatic perspective view with a portion exploded of asignal generating apparatus embodying the invention,

FIG. 2 is a sectional view taken on line 2--2 of FIG. 1,

FIG. 3 is a sectional view similar to that of FIG. 2 showing the signalgenerating apparatus with its rotary member angularly displaced 90°,

FIG. 4 is a diagrammatic top plan view of another embodiment of thesignal generating apparatus,

FIG. 5 is a view similar to that of FIG. 4 showing the signal generatingapparatus with its rotary member angularly displaced by 90°, and withportions broken away,

FIG. 6 is a perspective view of the apparatus of FIG. 4,

FIG. 7 is a graph illustrating the hysteresis characteristic of abistable magnetic device, and

FIGS. 8A and 8B are graphs illustrating respectively wave forms andoutput signals provided by the signal generating apparatus.

Like references designate like parts throughout the several views.

FIGS. 1, 2 and 3 illustrate a signal generating apparatus 10 embodyingthe invention. The apparatus 10 includes a conducting means 12 formagnetic flux in a first circuit 14 having an "0" configuration. Theconducting means 12 includes a substantially "L" shaped portion 16, ofhigh permeability, such as provided by known ferromagnetic materials.The portion 16 rests on a plurality of non-magnetic blocks 18 positionedon a supporting surface 20. A second smaller substantially "L" shapedportion 22, of high permeability, is also supported on blocks 18 and hasan end spaced from an end of the portion 16 to provide between them agap 24 (see FIGS. 2 and 3). The other end of portion 22 is spaced fromthe other end of portion 16 to provide between them a space 26 (see FIG.1). The gap 24 is an air gap providing a permeability which is lowerthan that provided by the portions 16 and 22 of the first circuit 14.

A member 26 supported for rotation on a shaft 28 which extends throughthe surface 20, is positioned within the gap 24. The member 26 providesa substantially elongated horizontal element 30 of high permeability(see FIG. 3) for conducting magnetic flux in the first circuit 14. Whenthe member 26 is rotated 90° into the position illustrated in FIGS. 1and 2, a maximum air gap is provided between the portions 16 and 22providing minimum permeance. The rotation of member 26 between thepositions of maximum and minimum permeance provides a value of permeancewhich varies between the maximum and minimum values as a continuousfunction of the angular position of the member 26.

The space 26 between the portions 16 and 22 of the conducting means 12receives therein a coupling means 32 comprising a plurality of verticalsections made of a high permeability material and providing an opening34 into which is received a bistable magnetic device 36 and a signaldetecting coil 38 wound therealong. The grooves 40 at the ends of thecoupling means 32 receive therethrough the leads 42 of the coil. Theoperation of the bistable magnetic device 36 and its detecting coil 38will be explained in greater detail below.

The first circuit 14 for magnetic flux is shown by the arrows extendingin the counter clockwise direction along the portion 16, through the gap24, and the member 26 to the portion 22. The flux extends from theportion 22 through the coupling means 32 and bistable magnetic device 36back to the portion 16 to complete the path of substantially "0"configuration. The reluctance of the circuit 14 is maximized andminimized when the member 26 is positioned as shown respectively inFIGS. 2 and 3, and the reluctance of the circuit 14 varies between themaximum and minimum values as a continuous function of the angularposition of the member 26.

A second conducting means 44 provides a second magnetic circuit 46having an "8" configuration which includes a substantially "S" shapedportion 48 of high permeability. The portion 48 is supported byplurality of block 50 above the conducting means 12. A second portion 52of the conducting means 44 which is substantially "J" shaped issupported on non-magnetic blocks 54 under the portions 16 and 22 of thefirst conducting means 12.

Respective ends of the portions 48 and 52 are also present at the gap 24and space 26, the ends of the portion 48 being at a higher level thanthe ends of the portion 52 (see FIGS. 1 and 2). In the gap 24, themember 26 provides a pair of elongated elements 56 and 58 of highpermeability, one above the other (FIG. 2), which extend perpendicularlyto the extending direction of the element 30. The ends of the element 56extend upwardly to the level of the portion 48 of the second circuit 46,while the ends of the element 58 extend downwardly to the level of thelower second portion 52 of the conducting means 44.

With the member 26 positioned as shown in FIGS. 1 and 2, a magnetic pathin circuit 46 of maximum permeance is provided by the elements 56 and 58through the gap 24, while the gap 24 provides minimum permeance when themember 26 is in its position shown in FIG. 3. The permeance provided bythe elements 56 and 58 varies between the maximum and minimum values asa continuous function of the rotary position of the member 26. Themagnetic flux path of circuit 46 is shown by the dashed lines and arrowsand extends along the portion 48 of the second conducting means 44 tothe gap 24 and then through the elevated end of the upper element 56 ofmember 26 and the central portion of the element 30 into the lowerelement 58 and its lower end which is closest to the end of the portion52 at the gap 24. The magnetic path of circuit 46 continues along theportion 52 to its end joining coupling means 32, where it enters thecoupling means 32 and the bistable device 36 in a direction or senseopposite to the direction or sense of the flux of circuit 14, andreturns at the other side of the coupling means 32 to the higher end ofthe portion 48 to complete the "8" shaped magnetic path.

As noted in connection with the circuit 14, the rotation as shown byarrow 29 of the member 26, from its position shown in FIG. 1, increasesthe reluctance of the circuit 46 from its minimum value. The maximumreluctance is provided after a 90° rotation of the member 26 to itsposition shown in FIG. 3. At this time, the greatest air space ispresent between the spaced ends of the elements 48 and 52 of theconducting means 44 at the gap 24. As also noted before, the reluctancevaries between the minimum and maximum values as a function of theangular displacements of the shaft 28. However, the value of reluctanceprovided by the member 26 for the first circuit 14 is out of phase withthat provided for the second circuit 46, their respective minimum andmaximum values occurring at positions 90° apart. One minimum and onemaximum value of reluctance is obtained for each circuit with each 180°of rotation of the member 26, providing two minimum and two maximumvalues in each circuit 14 and 46 for each complete rotation of 360°.

An energizing solenoid coil is provided having a winding 59 about theportions 16 and 48 of the conducting means 12 and 44 at a region wherethey extend over each other. The winding 59 provides a magnetic fieldfor inducing magnetic flux in the circuits 14 and 46. At the region ofthe winding 59 the flux induced in each of the circuits 14 and 46 is inthe same direction or sense as illustrated by the dashed lines andarrows for the respective flux paths. The flux in the circuit 14 of theconducting means 12, thus, moves in a counter clockwise direction in its"0" configuration path extending through the coupling means 32 and thebistable magnetic device 36 contained therein. On the other hand, amagnetic circuit 46 provided by the conducting means 44 which has an "8"configuration, crosses over itself and is presented in the oppositedirection or sense through the coupling means 32 and the bistablemagnetic device 36.

Since the reluctance in each of the circuits 14 and 46 of the conductingmeans 12 and 44 varies between maximum and minimum values, the flux oftheir respective circuits also vary in a corresponding inverse manner.Because of the 90° displacement between the element 30 and the elements56, 58 of the member 26, the net flux through the coupling means 32increases to a maximum value in one sense, decreases to zero, and thenincreases to a maximum value in the opposite sense with the rotation ofthe member 26. Thus, the amplitude and sense of the flux lines to whichthe bistable magnetic device 36 is subjected, is a function of theangular position of the member 26, going through two complete cycles foreach revolution of the member 26.

The bistable magnetic device 28 may be of the type described in U.S.Pat. No. 3,820,090 issued June 25, 1974 entitled "Bistable MagneticDevice," and comprises a wire of general uniform composition having acentral relatively "soft" core portion and an outer relatively "hard"magnetized shell portion with relatively low and high coercivities,respectively. Such a wire or device 36 may be made by properly workhardening a homogeneous magnetic alloy to provide the relatively hardshell portion of high coercivity with respect to the central core. Thedevice provides a high energy state when its flux extends externally,and a low energy state when its flux is substantially internal. In thelow energy state the flux in the shell captures and has a return paththrough the core of the device. Switching of the bistable magneticdevice 36 occurs when the density of an applied external flux passesthrough a value which allows the applied flux to capture the core of thedevice from its shell. This results in a rapid increase in external fluxdensity known as the "Wiegand Effect." This effect is detected as anoutput pulse signal by the coil 38. This phenomenon is also explained indetail in the article entitled "Wiegand Wire: New Material ForMagnetic-Based Devices" by Philip E. Wignen in Electronics dated July10, 1975, and in the article entitled "Wiegand Pulses Break Through IntoNew Application" in Canadian Controls & Instrumentation dated December1977.

The hysteresis curve of FIG. 7 illustrates a magnetic switchingcharacteristic of the bistable magnetic device 36. However, theinvention may also utilize devices with other switching characteristicssuch as those illustrated in U.S. Pat. No. 3,820,090 and the notedarticle by Philip E. Wignen.

In considering the operation of the bistable magnetic device 32, theupwardly sloping portion 60 of FIG. 7 illustrates the change in magneticdensity B of the bistable device 36 with the increase of appliedmagnetic field intensity H. When the intensity H reaches the level 62, arapid change in flux density B in the upward positive direction occursdue to the switching of the bistable magnetic means 36. At this time,the flux density B represented as a negative value reduces to and passesthrough zero value and increases in the opposite direction to a highvalue of flux density B of opposite sense represented as a positivevalue in FIG. 7. This rapid transition is illustrated by the almostvertical line 64. The further increase of the magnetic field intensity Hin the positive direction results in a smaller increase in flux densityB as illustrated by the reduced slope of line 66. With the reduction ofthe magnetic field intensity H to zero value, and its increase in thenegative direction, a gradual reduction in flux density B takes place asillustrated by the slope of line 68. When the magnetic field intensity Hreaches a value in the negative direction shown at the point 70, a rapidchange in the flux density B again occurs as illustrated by the almostvertical line 72. At this time, the flux density B moves downwardlythrough zero value and increases in the opposite negative direction tothe level illustrated at 74. This rapid reversal of flux density B isthe second switching action during the hysteresis cycle establishing astate for the bistable magnetic device 32 with its magnetic fluxexternal and in the opposite direction. Continued increase in thenegative value of the magnetic field intensity H, results in a gradualincreasing in magnetic flux density B in the negative sense asillustrated by the line 60.

A new cycle for the hysteresis curve of FIG. 7 is initiated, when thenegative magnetic field intensity H approaches zero value and continuesto increase in the positive direction to the point 62. At this time, thebistable magnetic means 36, again switches its state. Thus, for eachincrease and decrease of magnetic intensity H first in one sense andthen in the opposite sense, the bistable magnetic means 36 rapidlychanges its external magnetic flux from a maximum value in one sense toa maximum value in an opposite sense. This results in the coil 38producing an output pulse signal for each flux reversal, one pulse beingpositive with respect to the other.

Refer to FIGS. 8A and 8B for an explanation in greater detail of theoperation of the signal generating apparatus 10. With a direct currentapplied to the coil 59, magnetic flux B is induced in the first andsecond circuits 14 and 46. The level of the magnetic field intensity His controlled by a current control means 76 (FIG. 1) allowing adjustmentof the maximum value of induced magnetic flux B. Rotation of the rotarymeans 26 periodically increases and decreases the reluctance in thecircuits 14 and 46 as a function of rotary position. This results in thevariation of magnetic flux in each of the respective circuits, with thefluxuation of the magnetic flux in one circuit being delayed by 90° withrespect to the other. The flux of each circuit passes through thecoupling means 32 in a direction opposite to that of the other. Theresultant flux density B and sense is represented by the curve 78 ofFIG. 8A. The positive portions 80 of the alternating curve representsthe variation of flux through the coupling means 32 and the bistabledevice 36 in the direction of circuit 14, while the negative portions 82of the curve 78 represents the net magnitude of flux in the oppositedirection of circuit 46. The pair of horizontal dashed lines 84 and 86represent the respective levels of flux density B_(t) in the sense ofcircuits 14 and 46 which trigger a transition of state of the bistabledevice 36 as the flux intensity increases in the same sense. The fluxdensity B_(t), which is derived from the field of the energizing coil59, is related to the value of the field intensity H and results in thetransition of the bistable device 36 from one of its states to the otherillustrated in FIG. 7. The rapid change in flux about the bistablemagnetic device 36 which takes place with each such transition isdetected by the coil 38. This results in the delivery of a pulse 88 to asignal processing means 90 (FIG. 1). The pulses 88 are shown on thegraph of FIG. 8B to correspond to the transition points for the positiveportions 80 of the curve 78.

As the rotary member 26 changes position by rotation in the counterclockwise direction as illustrated by the arrow 29, a maximum ofmagnetic flux is provided at the coupling means 32 when the element 30is in alignment with the ends of the portions 16 and 22 (FIG. 3) forproviding minimum reluctance in the circuit 14. As the rotary means 26continues its movement in the counter clockwise direction, reluctance inthe circuit 14 increases while that in the circuit 46 decreases to apoint where they are substantially equal resulting in cancellation offlux at the coupling device 32. This is illustrated in FIG. 8A at thepoint where the positive portion 80 of the curve 78 passes over to thenegative portion 82 of the curve 78. Continued rotary motion of themember 26, brings the elements 56 and 58 closer into alignment with theportions 48 and 52 of circuit 48 decreasing its reluctance. This resultsin an increase in flux density B at the coupling 32 in the opposite (ornegative) direction as illustrated by the portions 82 of the curve 78 inFIG. 8A. When the level of the magnetic flux reaches the triggeringlevel-B_(t) illustrated by the dashed line 86, the bistable magneticdevice 32 alters its magnetic state. This results in a rapid change offlux in the direction opposite to that of its last transition producinga negative-going pulse 90 at corresponding times illustrated in FIG. 8B.In this manner, each revolution of the member 26 produces four outputpulses which are delivered by the detecting coil 38 to the signalprocessing means 90. The output pulses include two sets of alternatelyoccurring positive and negative pulses 88 and 90.

The timing or position of the output pulses may be controlled by theamplitude of the direct current delivered to the energizing coil 59 bythe current control means 76. Thus, if DC current is reduced, this willresult in a reduced magnetic flux B through the coupling means 32 asrepresented by the dashed curve 92 of FIG. 8A. The positive and negativepeak values although reduced, however, are sufficiently high to exceedthe magnetic flux triggering levels B_(t) (shown by the lines 84 and 86)required for providing output signals by the bistable magnetic device 36and detecting coil 38. However, a longer time is required for thenegative-going and positive-going portions of the curve 92 to crosstheir respective triggering levels B_(t). This results, in theproduction of the delayed or displaced output signals 88' and 90' shownby dashed lines in FIG. 8B. Thus, by controlling the level ofenergization of the winding 59, the output signals produced anddelivered to the signal processing means 90 may be advanced anddisplaced as desired. The delivery of output pulses 88 and 90 alsocorrespond to particular angular positions of the shaft 28 of the rotarymember 26. The output signals delivered by the coil 38, thus, indicatesthe angular positions of the shaft 28. Particular angular positions ofthe shaft 28 may also be selected by varying the amplitude of thecurrent delivered to the winding 59 of energizing coil.

For illustrating a particularly useful application of the signalgenerating means 10, the shaft 28 of the member 26 may be coupled forrotation in synchronism with the crank shaft of an internal combustionengine. For the embodiment illustrated, the energizing coil 38 willdeliver four output signals for each rotation. Such output signals maybe rectified by the signal processing means 90 and delivered to anignition system such as previously described for providing spark signalsby means of a usual distributor to the spark plugs of a four cylinderengine. The control means 76 by being made to respond to the rate ofrotation and load of the engine, will control the advance of the outputsignals delivered by the signal processing means 90 as alreadydescribed.

FIGS. 4 to 6 disclose a signal generating apparatus 100 which is amodified form of the apparatus 10. A conducting means 102 for magneticflux is provided by a portion 104 providing a path of high permeability,and a rotary member 106 providing paths of alterable permeance forvarying the reluctance of the conducting means 102. The portion 104 ofthe conducting means 102 includes first and second sections 108 and 110which are each substantially "U" shaped and have a high permeability, asprovided by well known ferromagnetic materials. The two ends of section108 provide pole pieces 112 and 114, while the ends of section 110provide pole pieces 116 and 118. The pole pieces 112, 114, 116 and 118are arranged in a clockwise direction about and shaped to defining acircumference which is proximate to the outer cylindrical surface 123 ofthe rotary member 106. The section 108 receives about it, a winding 59'of a solenoid coil which is energized by a direct current signal fromcurrent control means 76 as explained in connection with the apparatus10. A bistable magnetic device 36 and signal detecting coil 38 isreceived by section 110 of the conducting means 102 for deliveringoutput signals to the signal processing device 90 as previouslydescribed.

The pole pieces 114 and 118 of sections 108 and 110 of portion 104 arepositioned essentially diagonally opposite to each other and on the samelevel, while the pole pieces 112 and 116 are also positioned diagonallyopposite to each other but are on a lower level as clearly shown in FIG.6.

The rotary member 106 which is substantially cylindrical inconfiguration may have a body made of a non magnetic material and isprovided with first and second pairs of magnetic flux conductingelements 120 and 122. The pair of elements 120 are positioneddiametrically opposite to each other at and extending along theperiphery 123 of the member 106. The elements 120 each have anintermediate vertical portion 124, joined with a leading portion 126 atthe lower level of the pole pieces 112 and 116, and a trailing portion128 at the upper level of pole pieces 114 and 118. Thus, when the rotarymember 106 is positioned as shown in FIGS. 4 and 6, a flux path 14' isprovided. The path 14' is illustrated in FIG. 4 by the dashed lines andthe arrows showing direction of flux along the section 108 and from itslower pole piece 112, through one of the pair of elements 120 of therotary member 106. The path continues from the element 120 to the upperpole piece 118 of the section 110, along section 110 in the counterclockwise direction through the bistable magnetic device 36 to which itis coupled as previously described, and to the pole piece 116. The fluxpath then passes from the lower pole piece 116 to the other proximatelypositioned element 120 back to the first section 108 through its polepiece 114 at the upper level. Thus, with magnetic flux induced by thewinding 59', a circuit of magnetic flux is provided having asubstantially "0" configuration. As the rotary body 106 rotates in aclockwise direction as indicated by the arrow 130, the trailing portion128 of each of the sections 120 moves away from its upper level polepieces 114, 118 increasing the air gap therebetween and correspondinglythe reluctance of the circuit 14' from the minimum value provided by themember 106 in its position illustrated in FIGS. 4 and 6.

As the member 106 continues to rotate in a clockwise direction through90° the second pair of elements 22 comprising a horizontal element 132positioned below a horizontal element 134 move towards and into theirpositions shown in FIG. 5. The elements 132 and 134 extend diametricallyproviding enlarged opposite ends at the periphery of the member 106. Theends of the element 132 are at the lower level of the pole pieces 112,116 while the ends of the element 134 are at the upper level of the polepieces 114, 118. The elements 132 and 134 are spaced from each other bythe non magnetic material of the body of the rotary member 106, and thelower element 132 is displaced 45° in the clockwise direction, withrespect to the upper element 134.

With the member 106 positioned as shown in FIG. 5, the flux provided bythe energizing winding 59' flows in a magnetic circuit 46' in thedirection along the path indicated by the dashed lines and arrows. Theflux passes from the lower pole piece 112 of section 108 to theproximate end of the element 132 and through it to its other end and theproximate pole piece 116. Similarly, the element 134 which is displacedcounter-clockwise with respect to the element 132 completes a pathbetween the upper pole pieces 118 and 114 at the upper level provided atthe top of the rotary member 106. A low reluctance path is thus providedfor the circuit 46' which crosses over between diagonally opposite polepieces 112 and 116 and pole pieces 114 and 118 to provide magnetic fluxin a sense through the section 110 (clockwise direction) which isopposite to the sense of magnetic flux provided by the circuit 14'.

As the rotary member 106 continues to rotate in the clockwise direction,the reluctance provided to the circuit 46' increases (while thereluctance in the circuit 14' decreases) unit it becomes maximum againafter a displacement of 90° from its position shown in FIG. 5. Thus,with a complete rotation of 360°, the circuit 14' having the "0"configuration goes through variations providing two minimum reluctance(maximum flux density) conditions, while the circuit 46' goes throughsimilar variations in reluctance and flux density delayed by 90°. Sincethe "8" configuration flux path of circuit 46' provides magnetic fluxwith a sense which is opposite to that provided by the circuit 14' insection 110, the variation of the combined total flux at the bistabledevice 36 is also represented by the curves 78 and 92 of FIG. 8A.

Because of differences in the configuration of the pair of elements 120when compared to the pair of elements 122, an enlarged air gap 136 isprovided between the lower pole pieces 112, 116 and the outercylindrical surface 123 of the member 106 to compensate for and equalizethe positive and negative portions 80 and 82 of the magnetic fluxvariations of curves 78 and 92 of FIG. 8A. The gaps 136 have the effectof controlling the degree of change in reluctance of the circuit 14' asthe leading edges 126 of the elements 120 approach the pole pieces 112,116 to provide a configuration of the positive-going portion of thecurve 80 associated the flux of circuit 14' so that it closely matchesthe configuration of the negative-going portion of the wave 82associated with the flux of the circuit 46'. This is important forobtaining equally spaced pulses 88 and 90. Of course, other means mayalso be utilized for achieving this purpose.

For increasing the efficiency of the magnetic path 14' and minimizingleakage of magnetic flux, a pair of electromagnets 140 may be providedbetween the adjacent pole pieces 112 and 118, and the adjacent polepieces 114 and 116. The electromagnets 140 are positioned to providemagnetic poles inducing flux in a direction opposite to the direction ofthe path of flux flow 14' through the elements 120. Thus, when theelements 120 are displaced from their position between respectiveadjacent pole pieces 112 and 118, and adjacent pole pieces 114 and 116,the electromagnets 140 act to oppose magnetic flow therebetween. Theminimizing of leakage is important when magnetic flux is decreasing inthe circuit 14' and increasing in the circuit 46'. At such time, themagnetic flux flow is directed by the cross paths of the elements 132,134 to opposite pole pieces rather than to adjacent pole pieces. Theelectromagnets 140 may also be provided with increased magnetic flux foropposing leakage flux when the maximum flux level is increased by thecurrent control means 76. This can be achieved by energizing theelectromagnets 140 with direct current derived from the current controlmeans 76. In this way, when the level of current to the energizingwinding 59' is increased by the current control means 76, the current tothe electromagnets 140 will also be increased for opposing increasedleakage flux.

In order to oppose leakage of flux between the cross elements 132 and134 at their cross over point, a permanent magnet 142 is provided withinthe rotary member 106 at its center. The permanent magnet 142 ispositioned between the elements 132 and 134 to provide magnetic flux ina direction which is opposite to the direction of leakage flux betweenthe elements 132, 134. Thus, if the flux flow provided by the lowerelement 132 represents a north pole at the center region, and thedirection of the flux flow in the upper element 134 represents a southpole, the magnet 142 is positioned with its north pole proximate to theelement 132 and its south pole proximate to the element 134.

The signal generating apparatus 100 also illustrates the use of a secondbistable magnetic device 38' which may be similar to the bistable device38. The device 38' generates an output signal 144 for each revolution ofthe rotary member 106 as shown in FIG. 8B. Such marker signal 144 isuseful in determining the sequence of output signals 88 and 90 generatedduring a complete revolution of the rotary member 106. For this purpose,the bistable magnetic device 38' is secured in a substantially verticalposition to the vertical portion 124 of one of the elements 120 forcoupling it with the magnetic flux which periodically flows through theelements 120 when they are respectively positioned between the polepieces 116 and 114 and the pole pieces 112 and 118. An opposite magneticfield is provided, as by a vertically positioned magnet 146 (FIG. 5)positioned just ahead of the pole piece 114 for triggering the device38' to one of its states and conditioning it for being triggered to itsother state when it is between pole pieces 114 and 116. Thus, when themagnetic flux increases in the circuit 14' and flows through the element120, with which the bistable magnetic device 38' is associated, thedensity of magnetic flux increases to the point at which it triggers achange of state of the device 38'. With the change of the state, a rapidchange in the flux of the magnetic device 38' occurs providing the"Wiegand Effect." This results in inducing an output voltage signal inthe winding of a detecting coil, such as the winding of theelectromagnet 140, which is positioned proximate to the magnetic device38'. Sensing output signals from the device 38', provides the markersignal 144 occurring at the same position once during each revolution ofthe rotary member 106. The delivery of such output marker signals 144also serves to determine the absolute position of the shaft 28' and ofthe output pulses 88 and 90 which follow. The output signals 88 and 90may thus be identified and related to signals for particular cylinderswhen utilized in an ignition system for an internal combustion engine.

The signal generating apparatus 100, thus, operates in a manner similarto that described in connection with the apparatus 10 to produce varyingmagnetic flux and output signals as illustrated respectively in FIGS. 8Aand 8B. The means 100 also provides utility for determining variouspositions of its shaft 28' as well as rotary positions of other deviceswhich may be connected thereto. By adjusting of the energized current toits winding 59' it may also select various positions at which outputsignals are delivered to its signal processing means 90. This device,may also be used, as previously noted, in connection with ignitionsystems of automobiles with internal combustion engines for initiatingsparks to the cylinders of an automobile and providing advance sparkcontrol.

Of course, it is noted that the apparatuses 10 and 100 may be modifiedto provide output signals of more or less than the four pulses perrevolution provided by their rotary members 26 and 106, respectively.Thus, for example the number of elements 56, 58 of the rotary member 26of apparatus 10, and the number of elements 120, 122 of the rotarymember 106 of apparatus 100, may be increased to increase the number ofoutput pulses. The rotary members 26 and 106 may also be coupled torotate at higher or lower rates with respect to the crank shaft of aninternal combustion engine or other device for providing the requirednumber of sparks or signals for each rotation.

Although several embodiments of the invention have been described indetail, it will be obvious to those skilled in the art that theinvention disclosed may be modified to meet particular designcircumstances, without substantial departure from the essence of theinvention.

What is claimed is:
 1. A signal generating apparatus comprising abistable magnetic device which alters its magnetic state when thedensity of magnetic flux to which it is subject passes through apredetermined value, detecting means providing an output signalresponsive to a change in magnetic state of said bistable device,conducting means for magnetic flux for subjecting said bistable magneticdevice to conducted magnetic flux, said conducting means comprising afirst portion providing a path of high permeability and a second portionproviding a path of alterable permeance for varying the reluctance ofsaid conducting means and the density of magnetic flux to which saidbistable device is subject, the conducting means providing a firstcircuit for magnetic flux with a non cross-over "0" configuration andsecond circuit with a cross-over "8" configuration for subjecting saidbistable device to magnetic flux of opposite senses, and an energizingmeans providing a controllable magnetic field for inducing magnetic fluxin the first and second circuits of said conducting means and providinga flux density sufficient to alter the state of said bistable devicewith the variation of reluctance of said conducting means.
 2. Theapparatus of claim 1 in which the path of the second portion of saidconducting means includes a variable length gap of reduced permeabilityfor varying the reluctance of said conducting means. PG,33
 3. Theapparatus of claim 2 in which the variable length gap is provided by afixed gap of reduced permeability and a member providing a path of highpermeability movable within said fixed gap.
 4. The apparatus of claim 3in which said member is rotatable for periodically varying thereluctance provided by said second portion.
 5. The apparatus of claim 4in which said member includes at least one element having an elongatedconfiguration providing a minimum value of reluctance when it is in oneof its angular positions aligned with the flux path of said secondportion and providing a maximum value of reluctance when it is in anangular position intermediate its aligned positions, said memberproviding reluctance values varying between said minimum and maximumvalues as a continuous function of its angular position.
 6. Theapparatus of claim 5 in which said energizing means includes anenergizing coil wound about the first portion of said conducting meansand an energizing source providing direct current to said coil, thevalue of the direct current provided to said coil being adjustable fordetermining an angular position of said member at which said bistabledevice is subject to said predetermined value of flux density foraltering its magnetic state and said detecting means provides an outputsignal.
 7. The apparatus of claim 6 in which said member includes shaftmeans adapted to be rotatively driven in synchronism with an internalcombustion engine for providing spark timing signals derived from saiddetecting means, and including a current control means varying the valueof the direct current provided to said coil for advancing and retardingthe occurrence of the output signals of said detecting means withrespect to the angular position of said member for being responsive tothe requirements of an internal combustion engine.
 8. The apparatus ofclaim 6 or 7 in which ferromagnetic material provides the path of highpermeability and air provides the path of reduced permeability of saidconducting means, the first and the second portions are arranged toprovide a series path for the magnetic flux induced by said coil, andsaid bistable device is subject to the magnetic flux in the path of thefirst portion of said conducting means.
 9. A signal generating apparatuscomprising a bistable magnetic device which alters its magnetic statewhen the density of magnetic flux to which it is subject passes througha predetermined value, detecting means providing a output signalresponsive to a change in magnetic state of said bistable device,conducting means for magnetic flux for subjecting said bistable magneticdevice to conducted magnetic flux, said conducting means comprisingfirst and third portions each providing a path of high permeability anda second portion providing a path of alterable permeance for varying thereluctance of said conducting means and the density of magnetic flux towhich said bistable device is subject, first and second circuits formagnetic flux each comprising a respective one of said conducting meansincluding said first, second and third portions, and an energizing meansproviding a controllable magnetic field for inducing magnetic flux insaid conducting means and providing a flux density sufficient to alterthe state of said bistable device with the variation of reluctance ofsaid conducting means, said energizing means inducing magnetic flux inthe first and second circuits of said conducting means with the magneticflux having opposite senses respectively in the third portions of saidfirst and second circuits, said bistable device being subject to thecombined magnetic flux of the third portions of the first and secondcircuits of said conducting means.
 10. The apparatus of claim 9 in whichthe path of each of the second portions of said first and secondcircuits is provided with a variable length gap of reduced permeabilityfor varying the reluctance of their respective circuits.
 11. Theapparatus of claim 10 in which the variable length gap of each of saidsecond portions is provided by a fixed gap of reduced permeability and amember providing a path of high permeability movable within each of saidfixed gaps.
 12. The apparatus of claim 11 in which said member isrotatable for periodically varying the reluctances provided by saidsecond portions.
 13. The apparatus of claim 12 in which said memberprovides at least one element of high permeability for each gap, eachelement having an elongated configuration and providing a minimum valueof reluctance when it is in one of its angular positions aligned withthe flux path of its second portion and providing a maximum value ofreluctance when it is in an angular position intermediate its alignedpositions, each element of said member providing reluctance valuesvarying between said minimum and maximum values as a continuous functionof its angular position, the elements of said member providing maximumreluctance for one of said circuits while the other circuit has minimumreluctance for alternately subjecting said bistable device to varyingmagnetic flux of opposite senses with the rotation of said member. 14.The apparatus of claim 13 in which at least a part of the first portionsof said circuits are proximately positioned, said energizing meansincludes an energizing coil wound about the proximate parts of the firstportions of said conducting means providing therein magnetic flux of thesame sense, and an energizing source providing direct current to saidcoil, the value of direct current provided to said coil being adjustablefor determining the angular positions of said member at which saidbistable device is subject to said predetermined value of flux densityfor altering its magnetic state and said detecting means provides outputsignals.
 15. The apparatus of claim 14 in which said member includes ashaft means adapted to be rotatively driven in synchronism with aninternal combustion engine for providing spark timing signals derivedfrom said detecting means, and including a current control means varyingthe value of the direct current provided to said coil for advancing andretarding the occurrence of the output signals of said detecting meanswith respect to the angular position of said member for being responsiveto the requirements of an internal combustion engine.
 16. The apparatusof claim 14 or 15 in which ferromagnetic material provides the paths ofhigh permeability and air provides the paths of reduced permeability ofsaid conducting means, each circuit has its first, second and thirdportions arranged to provide a series path for magnetic flux induced init by said coil, the second portions are positioned proximate to eachother with their gaps in alignment for receiving said member, said firstcircuit provides a non corss-over "0" configuration path for magneticflux while said second circuit provides a cross-over "8" configurationpath, and the third portions are positioned proximate to each other andinclude a coupling means receiving and subjecting said bistable deviceto the magnetic flux of each of said third portions.
 17. A signalgenerating apparatus comprising a bistable magnetic device which altersits magnetic state when the density of magnetic flux to which it issubject passes through a predetermined value, detecting means providingan output signal responsive to a change in magnetic state of saidbistable device, conducting means for magnetic flux for subjecting saidbistable magnetic device to conducted magnetic flux, said conductingmeans comprising a first portion providing a path of high permeabilityand a second portion providing a path of alterable permeance for varyingthe reluctance of said conducting means and the density of magnetic fluxto which said bistable device is subject, the first and second portionsof said conducting means providing first and second circuits formagnetic flux, the first portion of said conducting means having firstand second sections each with first and second pole ends spaced fromeach other about and defining a circumference, said second portionproviding said first circuit with paths for magnetic flux directlybetween the pole ends of different sections which are adjacentlypositioned along said circumference and providing said second circuitwith paths for magnetic flux which cross-over each other between poleends of different sections which are non-adjacently positioned alongsaid circumference, said second portion conditionally providing thepaths of said first and second circuits with high and reducedpermeabilities, and an energizing means providing a controllablemagnetic field for inducing magnetic flux in said conducting means andproviding a flux density sufficient to alter the state of said bistabledevice with the variation of reluctance of said conducting means, saidenergizing means inducing magnetic flux in a first sense in the firstsection of said conducting means, while in the second section the firstcircuit provides induced magnetic flux in the first sense and the secondcircuit provides induced magnetic flux in a second opposite sense, saidbistable device being subject to the combined magnetic flux of saidfirst and second circuits in the second setion of said conducting means.18. The apparatus of claim 17 in which said second portion includes amember which is positioned within said circumference proximate to thepole ends of said first portion and is rotatable for altering thepermeability of the first and second paths and varying the reluctance ofsaid first and second circuits.
 19. The apparatus of claim 18 in whichsaid member has a plurality of elements of high permeability providing afirst pair and a second pair of elements, said member providing aminimum value of reluctance for said first circuit when in a firstangular position aligning the first pair of elements along the pathsbetween the pole ends of different sections which are adjacentlypositioned along said circumference, said member providing a minimumvalue of reluctance for said second circuit when in a second angularposition aligning the second pair of elements along the paths whichcross-over each other between pole ends of different sections which arenon-adjacently positioned along said circumference, said memberproviding a maximum value of reluctance for said first and secondcircuits respectively when said member is correspondingly in its secondand first positions, said member providing reluctance values varyingbetween said minimum and maximum values respectively for said first andsecond circuits as continuous functions of its angular position.
 20. Theapparatus of claim 19 in which each of the first pair of elements ofsaid member extends along a segment of said circumference and saidsecond pair of elements cross-over each other and have spaced ends atopposite locations at said circumference between said first pair ofelements, the first pair of elements are respectively along and span thespace between the pole ends of different sections of said first portionwhich are adjacently positioned along said circumference when saidmember is in its first position and are removed from said space whensaid member is in its second angular position, the second pair ofelements which cross-over each other are spaced from each other and arepositioned between and have their ends respectively in proximaterelationship to the pole ends of different sections which arenon-adjacently positioned along said circumference when said member isin its second position and are removed from said proximate relationshipwith the pole ends when said member is in its first angular position.21. The apparatus of claim 20 in which the first pole ends of saidsections provide pole pieces substantially diagonally across from eachother at a first level about said circumference and said second poleends provide pole pieces substantially diagonally across from each otherat a second level below said first level about said circumference, thefirst pair of elements of said member extend between said first andsecond levels of said pole pieces for conditionally providing paths ofhigh permeability between pole pieces of pole ends of different sectionsof said first portion which are adjacently positioned along saidcircumference, the second pair of elements each extend along arespective one of said first and second levels for conditionallyproviding a path of high permeability between the pair of pole piecescorresponding to its level.
 22. The apparatus of claim 21 which includesmagnetic means providing one or more magnetic fields inducing magneticflux having a sense opposite to the sense of leakage flux between saidpole pieces outside of said elements.
 23. The apparatus of claim 22 inwhich said magnetic means includes at least one electro magnet energizedby said energizing means positioned along said circumference betweenadjacent pole pieces of different sections, and a magnet within saidmember between the elements of the second pair of elements and with itspoles proximate to respective ones of said second pair of elements. 24.The apparatus of claim 17 in which said energizing means includes anenergizing coil wound about the first section of said conducting meansand an energizing source providing direct current to said coil, thevalue of direct current to said coil being adjustable for determiningthe angular position of said member at which said bistable device issubject to said predetermined value of flux density for altering itsmagnetic state and said detecting means provides an output signal. 25.The apparatus of claim 24 in which said second portion includes a memberwhich is positioned within said circumference proximate to the pole endsof said first portion and is rotatable for altering the permeability ofthe first and second paths for varying the reluctance of said first andsecond circuits, and includes shaft means adapted to be rotativelydriven in synchronism with an internal combustion engine for providingspark timing signals derived from said detecting means, and including acurrent control means varying the value of the direct current providedto said coil for advancing and retarding the occurrence of the outputsignals of said detecting means with respect to the angular position ofsaid member for being responsive to the requirements of an internalcombustion engine.
 26. The apparatus of claim 25 which includes anothersaid bistable magnetic device mounted for rotation with said member,said detecting means providing a plurality of output signals from thefirst said bistable magnetic device and one output signal from the lastsaid bistable device for each complete rotation of said member.
 27. Theapparatus of claim 23 or 25 in which ferromagnetic material provides thepaths of high permeability and air provides the paths of reducedpermeability of said conducting means, the first and second portions ofsaid conducting means are arranged to provide each of said circuits witha series path for magnetic flux induced in it by said coil, said firstcircuit provides a non cross-over "0" configuration path for magneticflux while said second circuit provides a cross-over "8" configurationpath, and which includes a coupling means for subjecting said bistabledevice to the magnetic flux in the second section of said conductingmeans.